From 23e368883b01ebb08ba2df56db91f19f26cf990d Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 14 Mar 2022 09:10:12 +0200
Subject: [PATCH] Use a per-camera cache in ZSortedScene

It's very common to have multiple cameras in a scene due to effects like
shadow and environment maps.  Using a single cache for all of them is
detrimental since the order will be different for each.
---
 source/render/zsortedscene.cpp | 45 +++++++++++++++-------------------
 source/render/zsortedscene.h   |  6 +----
 2 files changed, 21 insertions(+), 30 deletions(-)

diff --git a/source/render/zsortedscene.cpp b/source/render/zsortedscene.cpp
index 9c56f26e..bdce8aa9 100644
--- a/source/render/zsortedscene.cpp
+++ b/source/render/zsortedscene.cpp
@@ -14,8 +14,8 @@ void ZSortedScene::add(Renderable &r)
 	if(i==content.end() || *i!=&r)
 	{
 		content.insert(i, &r);
-		if(!sorted_cache.empty())
-			sorted_cache.push_back(&r);
+		for(auto &kvp: sorted_cache)
+			kvp.second.push_back(&r);
 	}
 }
 
@@ -39,26 +39,16 @@ void ZSortedScene::set_reference(DepthReference r)
 	reference = r;
 }
 
-void ZSortedScene::populate_cache() const
-{
-	if(sorted_cache.empty() && !content.empty())
-	{
-		sorted_cache.reserve(content.size());
-		sorted_cache.insert(sorted_cache.end(), content.begin(), content.end());
-	}
-}
-
 void ZSortedScene::setup_frame(Renderer &renderer)
 {
-	populate_cache();
-	for(const SortedRenderable &r: sorted_cache)
-		r.renderable->setup_frame(renderer);
+	for(Renderable *r: content)
+		r->setup_frame(renderer);
 }
 
 void ZSortedScene::finish_frame()
 {
-	for(const SortedRenderable &r: sorted_cache)
-		r.renderable->finish_frame();
+	for(Renderable *r: content)
+		r->finish_frame();
 }
 
 void ZSortedScene::render(Renderer &renderer, Tag tag) const
@@ -66,22 +56,27 @@ void ZSortedScene::render(Renderer &renderer, Tag tag) const
 	if(content.empty())
 		return;
 
-	populate_cache();
-
 	const Camera *camera = renderer.get_camera();
 	if(!camera)
 	{
-		for(const SortedRenderable &r: sorted_cache)
-			r.renderable->render(renderer, tag);
+		for(Renderable *r: content)
+			r->render(renderer, tag);
 		return;
 	}
 
+	vector<SortedRenderable> &cache = sorted_cache[camera];
+	if(cache.empty() && !content.empty())
+	{
+		cache.reserve(content.size());
+		cache.insert(cache.end(), content.begin(), content.end());
+	}
+
 	const Vector3 &camera_pos = camera->get_position();
 	const Vector3 &look_dir = camera->get_look_direction();
 	float radius_factor = reference-1.0f;
 	float sign = 1.0f-order*2.0f;
 
-	for(SortedRenderable &r: sorted_cache)
+	for(SortedRenderable &r: cache)
 	{
 		r.in_frustum = camera->is_in_frustum(*r.renderable);
 		if(!r.in_frustum)
@@ -99,18 +94,18 @@ void ZSortedScene::render(Renderer &renderer, Tag tag) const
 			r.depth = 0;
 	}
 
-	for(auto i=sorted_cache.begin(), j=i; i!=sorted_cache.end(); ++i)
+	for(auto i=cache.begin(), j=i; i!=cache.end(); ++i)
 		if(i->in_frustum)
 		{
 			if(i!=j)
 				swap(*i, *j);
 
-			if(j!=sorted_cache.begin() && *j<*(j-1))
+			if(j!=cache.begin() && *j<*(j-1))
 			{
 				SortedRenderable sr = *j;
 				auto k = j-1;
 				*j = *k;
-				while(k!=sorted_cache.begin() && sr<*(k-1))
+				while(k!=cache.begin() && sr<*(k-1))
 				{
 					*k = *(k-1);
 					--k;
@@ -121,7 +116,7 @@ void ZSortedScene::render(Renderer &renderer, Tag tag) const
 			++j;
 		}
 
-	for(auto i=sorted_cache.begin(); (i!=sorted_cache.end() && i->in_frustum); ++i)
+	for(auto i=cache.begin(); (i!=cache.end() && i->in_frustum); ++i)
 		i->renderable->render(renderer, tag);
 }
 
diff --git a/source/render/zsortedscene.h b/source/render/zsortedscene.h
index 778b097e..be23ac27 100644
--- a/source/render/zsortedscene.h
+++ b/source/render/zsortedscene.h
@@ -48,7 +48,7 @@ private:
 	std::vector<Renderable *> content;
 	SortOrder order = BACK_TO_FRONT;
 	DepthReference reference = FURTHEST;
-	mutable std::vector<SortedRenderable> sorted_cache;
+	mutable std::map<const Camera *, std::vector<SortedRenderable> > sorted_cache;
 
 public:
 	virtual void add(Renderable &);
@@ -60,10 +60,6 @@ public:
 	/// Sets the reference point for sorting.  Default is furthest from camera.
 	void set_reference(DepthReference);
 
-private:
-	void populate_cache() const;
-
-public:
 	virtual void setup_frame(Renderer &);
 	virtual void finish_frame();
 
-- 
2.43.0